/***************************************************************************************
 * Copyright (c) 2021 Arthur Milchior <arthur@milchior.fr>                              *
 *                                                                                      *
 * This program is free software; you can redistribute it and/or modify it under        *
 * the terms of the GNU General Public License as published by the Free Software        *
 * Foundation; either version 3 of the License, or (at your option) any later           *
 * version.                                                                             *
 *                                                                                      *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY      *
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A      *
 * PARTICULAR PURPOSE. See the GNU General Public License for more details.             *
 *                                                                                      *
 * You should have received a copy of the GNU General Public License along with         *
 * this program.  If not, see <http://www.gnu.org/licenses/>.                           *
 ****************************************************************************************/
package com.ichi2.utils

import java.util.HashMap
import java.util.HashSet

object HashUtil {
    /**
     * @param size Number of elements expected in the hash structure
     * @return Initial capacity for the hash structure. Copied from HashMap code
     */
    private fun capacity(size: Int): Int = ((size / .75f).toInt() + 1).coerceAtLeast(16)

    fun <T> hashSetInit(size: Int): HashSet<T> = HashSet(capacity(size))

    @KotlinCleanup("return mutableMap")
    fun <T, U> hashMapInit(size: Int): HashMap<T, U> = HashMap(capacity(size))
}

/** Provides a hashcode given a series of ints */
fun hash(vararg values: Int): Int = values.fold(0) { acc, value -> 31 * acc + value }
